Ultraviolet-infrared absorbent low transmittance glass

ABSTRACT

The ultraviolet/infrared absorbent low transmittance glass has an almost neutral color such as greenish gray, low visible light transmittance, low total solar energy transmittance, and low ultraviolet transmittance, and is suitable for a rear window of a vehicle and capable of protecting privacy. The glass consists of base glass including: 65 to 80 wt. % SiO 2 ; 0 to 5 wt. % Al 2 O 3 ; 0 to 10 wt. % MgO; 5 to 15 wt. % CaO wherein a total amount of MgO and CaO is between 5 and 15 wt. %; 10 to 18 wt. % Na 2 O; 0 to 5 wt. % K 2 O wherein a total amount of Na 2 O and K 2 O is between 10 and 20 wt. %; and 0 to 5 wt. % B 2 O 3 , and colorants including: 1.25 to 1.5 wt. % total iron oxide (T—Fe 2 O 3 ) expressed as Fe 2 O 3 ; 0.01 to 0.019 wt. % CoO; more than 0.0008 wt. % and equal to or less than 0.003 wt. % Se; and 0.055 to 0.1 wt. % NiO. The glass with a thickness between 2 and 5 mm has a visible light transmittance (YA) in a range from 10% to 25% using illuminant “A”, a solar energy transmittance in a range from 5% to 20% and an ultraviolet transmittance (Tuv) of not more than 15%.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation-in-part application of patent application Ser. No09/251,743 filed on Feb. 18, 1999 now abandoned.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to an ultraviolet/infrared absorbent lowtransmittance glass. More particularly, it relates to anultraviolet/infrared absorbent low transmittance glass which has analmost neutral color such as greenish gray shade and which has lowvisible light transmittance, low solar energy transmittance, and lowultraviolet transmittance, so that it is useful for windows of vehiclesor buildings particularly for a privacy protecting glass in a rearwindow of a vehicle.

Recently, a variety of glasses with ultraviolet/infrared absorptivity tobe used as a vehicle windshield have been proposed with the view ofpreventing degradation of luxurious interior materials and reducingcooling load of the vehicle. In view of privacy protection, glass withrelatively low visible light transmittance is preferably used for a rearwindow glass of a vehicle. Such kinds of glass include the followings.

For example, a dark gray colored infrared absorbent glass disclosed inJapanese Patent H7-29813B consists of soda-lime-silica glass includingcolorants consisting of 1.00 to 1.7 weight percent Fe₂O₃ (total iron),at least 0.27 weight percent FeO, 0.002 to 0.005 weight percent Se, and0.01 to 0.02 weight percent CoO. The glass exhibits luminoustransmittance less than 32 percent and total solar infraredtransmittance less than 15 percent at 3.9 mm thickness.

A dark gray colored glass disclosed in Japanese Patent H8-157232Aconsists of soda-lime-silica glass including colorants consisting of 0.8to 1.4 weight percent Fe₂O₃ (total iron), less than 0.21 weight percentFeO, 0.05 to 1.0 weight percent TiO₂, 0.02 to 0.05 weight percent CoO,and 0.0005 to 0.015 weight percent Se.

A neutral gray colored glass disclosed in claim 25 of U.S. Pat. No.5,393,593 consists of soda-lime-silica glass including colorantsconsisting of 1.00 to 2.2 weight percent Fe₂O₃ (total iron), at least0.20 weight percent FeO, 0.0005 to 0.005 weight percent Se, and 0.010 to0.030 weight percent CoO. The glass exhibits luminous transmittance lessthan 35 percent and total solar infrared transmittance less than 20percent at 3.9 mm thickness.

A glass disclosed in PCT (Japanese phase) H7-508971 consists ofsoda-lime-silica glass including colorants consisting of 1.3 to 2.0weight percent of Fe₂O₃ (total iron), about 0.01 to 0.05 weight percentof NiO, about 0.02 to 0.04 weight percent of Co₃O₄, about 0.0002 to0.003 weight percent of Se and having a ferrous iron value of 18 to 30weight percent and less than 0.53 of a light and shade coefficient.

In both the dark gray colored infrared absorbent glass disclosed inJapanese Patent H7-29813B and the neutral gray colored glass disclosedin U.S. Pat. No. 5,393,593, a great quantity of Se is used for providinga desirable color. Such a great quantity of Se is unpreferable for theenvironment because Se has toxicity and is easy to vaporize. The abovedark gray glass disclosed in Japanese Patent H8-157232A including 0.05to 1.0 weight percent TiO₂ as an essential component is unpreferablebecause TiO₂ is expensive to increase the batch cost.

The aforementioned glass includes selenium in high concentration toprovide optical properties, without essentially including nickel.

The glass disclosed in PCT (Japanese phase) H7-508971 is prepared fromstandard soda-lime-silica glass to which iron oxide, cobalt oxide,nickel oxide and selenium are added in a specific ratio. However, theglass composition disclosed therein has a great content of selenium andsmall amount of nickel oxide.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide anultraviolet/infrared absorbent low transmittance glass which has analmost neutral color such as greenish gray and which has low visiblelight transmittance, low solar energy transmittance and low ultraviolettransmittance so that it is useful for a window of a vehicle or abuilding particularly for a privacy protecting glass of a rear window ofa vehicle.

The ultraviolet/infrared absorbent low transmittance glass of thepresent invention consists of a base glass, that is, the majorconstituents comprising:

65 to 80 wt. % SiO₂;

0 to 5 wt. % Al₂O₃;

0 to 10 wt. % MgO;

5 to 15 wt. % CaO wherein a total amount of MgO and CaO is between 5 and15 wt. %;

10 to 18 wt. % Na₂O;

0 to 5 wt. % K₂O wherein a total amount of Na₂O and K₂O is between 10and 20 wt. %; and

0 to 5 wt. % B₂O₃, and a colorant including:

1.25 to 1.5 wt. % total iron oxide (T—Fe₂O₃) expressed as Fe₂O₃;

0.01 to 0.019 wt. % CoO;

more than 0.0008 wt. % and equal to or less than 0.003 wt. % Se; and

0.055 to 0.1 wt. % NiO.

When it is measured by using C.I.E. standard illuminant “A”, the glasswith a thickness between 2 and 5 mm has a visible light transmittance(YA) in a range from 10 to 25%, a solar energy transmittance (TG) in arange from 5 to 20% and an ultraviolet transmittance (Tuv) of less than15%.

In the present invention, the desired color shade can be obtained with asmaller amount of Se, which is desired to be decreased in contentbecause of its toxicity and volatility, and with a greater amount of NiOthan the amount conventionally required. It has been understoodconventionally that adding nickel to glass is unpreferable because offormation of nickel sulfide stones. However, the formation of nickelsulfide stones is more strongly dependent on the size of nickel grainsadded in the batch or redox of the glass than the concentration of NiO.When the concentration of NiO in the glass is too high, there is apossibility that NiO coagulates to form the nickel sulfide stones.However, when NiO is in a range defined by this invention, the desiredcolor can be obtained without producing the nickel sulfide stones.

PREFERRED EMBODIMENTS

The description will be made as regard to an ultraviolet/infraredabsorbent low transmittance glass composition. It should be noted thatcomponents will be represented with percentage by weight.

SiO₂(silica) is a principal component for forming skeleton of glass.Less than 65% SiO₂ lowers the durability of the glass and more than 80%SiO₂ raises the melting temperature of the glass so high.

Al₂O₃ is a component for improving the durability of the glass. Morethan 5% Al₂O₃ raises the melting temperature of the glass so high. Thepreferable range of Al₂O₃ is between 0.1% and 2%.

MgO and CaO improve the durability of the glass and adjust adevitrification temperature and viscosity of the glass during molding.More than 10% MgO raises the devitrification temperature. Less than 5%or more than 15% CaO raises the devitrification temperature of theglass. The durability of the glass is lowered when the total amount ofMgO and CaO is less than 5%, while the devitrification temperature isincreased when the total exceeds 15%.

Na₂O and K₂O prompt the glass to melt. The efficiency of promotion ofmelting becomes poor when Na₂O is less than 10% or the total of Na₂O andK₂O is less than 10%, while the durability of the glass is lowered whenNa₂O exceeds 18% or the total of Na₂O and K₂O exceeds 20%. K₂O ispreferable not to exceed 5% because of its expensive cost.

B₂O₃ is a component for improving the durability of the glass, promptingto melt, and yet enhancing the ultraviolet absorption. B₂O₃ should beless than 5%, since difficulties during molding are caused due to thevaporization of B₂O₃ when B₂O₃ exceeds 5%.

Iron oxide is present in the form of Fe₂O₃ and the form of FeO in theglass. Fe₂O₃ is a component for improving the ultraviolet absorptivityand FeO is a component for improving the heat rays absorptivity.

When the total amount of iron oxide (T—Fe₂O₃) expressed as Fe₂O₃ is lessthan 1.25%, the efficiency of ultraviolet and infrared absorptivitybecomes small so as not to provide desired optical properties. On theother hand, when T—Fe₂O₃ exceeds 1.5%, there is an unpreferablepossibility that the temperature around a crown of a glass meltingfurnace exceeds its refractory temperature due to absorption of the heatrays by the ferrous oxide. In addition, in case of successivelyproducing glasses by a glass melting furnace with T—Fe₂O₃ exceeding1.5%, long time is required to alter a glass composition in the furnace.

More than 1.25% T—Fe₂O₃ can offer preferably sufficient efficiency ofultraviolet and infrared absorptivity.

Fe₂O₃ has a function of particularly increasing the absorptivity inultraviolet range when glass is reinforced by air blast cooling. Thismeans that the glass of this invention can obtain enough efficiency ofultraviolet absorptivity without using expensive ultraviolet absorbentsuch as CeO₂ and TiO₂. When T—Fe₂O₃ is in the range mentioned above, thedesired color shade of the glass can be obtained after discoloration dueto the reinforcement process by air blast cooling.

When the FeO/T—Fe₂O₃ ratio (a weight of FeO expressed as Fe₂O₃ againstT—Fe₂O₃) is too low, the heat rays absorptivity can not be obtainedsufficiently because of a small amount of FeO. Many bubbles are alsoformed in the molten glass because the molten glass is relativelyoxidative so that the product yield is lowered. When the FeO/T—Fe₂O₃ratio is too high, the visible light transmittance is reduced and thecolor is of a blue tint. In addition, nickel sulfide stones aresometimes present in the molten glass because the molten glass isrelatively reductive. Too high ratio of FeO/T—Fe₂O₃ is also unpreferablesince it causes streaks with enough silica and silica scum.

In the present invention, the FeO/T—Fe₂O₃ ratio in a range between 0.15and 0.4 brings a green shade which is an almost neutral color havinghigh ultraviolet absorptivity and high heat rays absorptivity. In thiscase, values expressed as Fe₂O₃ are used for the content of FeO.

CoO is a component for forming an almost neutral color such as greenishgray shade by cooperating with Se and/or NiO, and Fe₂O₃ for controllingthe visible light transmittance. Less than 0.01% CoO can not form adesired color shade and makes the visible light transmittance too high.More than 0.019% CoO makes the color too blue tint and reduces thevisible light transmittance.

Se contributes a pink color, so that it reduces the excitation puritywith the aid of a complementary color of CoO. Less than 0.0008% Se cannot form a desired greenish gray shade, and more than 0.003% Se reducesthe visible light transmittance. When using Se, the content thereof ispreferable in a range between 0.0008% and 0.003%, preferably in a rangebetween 0.001% and 0.0018%.

NiO is a component for controlling the visible light transmittance andreducing the excitation purity as like as CoO. NiO has an absoptivity ina wide infrared range, so that it is a component for reducing the solarenergy transmittance as like as FeO. Less then 0.055% NiO can not form adesired color shade. To reduce the solar energy transmittance requires alarge amount of FeO which causes difficulties on the production of theglass. When NiO is more than 0.1%, nickel sulfide stones are sometimespresent in the product and the visible light transmittance is reduced.In addition, the obtained shade becomes too greenish. When using NiO,the content thereof is preferably in a range between 0.06% and 0.1%.

It is known that the coordination number of NiO varies according to therate of cooling glass so that the color of the glass varies. This isbecause the cooling varies the coordination number of oxide around Ni²⁺from 6 into 4 and thus varies the optical absorption. The absorption ofNi²⁺ with octahedral coordination exists around 430 nanometers so as tocontribute yellow to the glass, while the absorption of Ni²⁺ withtetrahedral coordination exists from 500 to 640 nanometers. Therefore,the excitation purity would be reduced to obtain the preferable shade byusing Ni²⁺ with tetrahedral coordination.

A windshield of a passenger car is normally reinforced by air blastcooling for safety. The reinforcement process by air blast coolingimproves the absorption of NiO with 4 coordinating atoms, and reducesthe visible light transmittance. Although the reinforcement process byair blast cooling reduces the absorption of visible lights, thevariations of NiO increases the absorption. The composition of the glassof the present invention is determined such that the optical propertiesof the glass after the reinforcement process fall in the desired range.

CeO₂ is a component for improving the ultraviolet absorptivity and ispresent in the form of Ce³⁺ or in the form of Ce⁴⁺ in glass.Particularly, Ce³⁺ is effective in absorbing ultraviolet with lessabsorptivity in the visible range. In the present invention, oxide ofCe³⁺ is also expressed in terms of CeO₂ and is included in the totalamount of CeO₂.

TiO₂ is a component for improving the ultraviolet absorptivityparticularly by interaction with FeO. TiO₂ can be added to improve theultraviolet absorptivity within such a range as not to lose the almostneutral color such as greenish gray shade, or to add a yellow tint inorder to obtain the desired color shade. The use of expensive CeO₂, TiO₂increases the cost so that it is not preferable to use more than 2%CeO₂, TiO₂.

One or more than two among MnO, V₂O₅, MoO₃, CuO, Cr₂O₃, and the like maybe added as colorant and SnO₂ within a rang from 0% to 1% in total maybe added as a reducing agent in such a range as not to lose middletransmittance and the almost neutral color such as greenish gray shade.To further securely prevent the formation of nickel sulfide stones, ZnOmay be added in a range from 0% to 1%.

In the present invention, the glass is preferable to be reinforced bythe air blasting. The desired color shade and optical properties areobtained in the reinforced process when the glass has the composition ofthe present invention comprising NiO and Fe₂O₃ in the specific amount.

In the reinforcement process, the glass plate produced from the moltenglass is reheated at 600 to 750° C. for 2 to 5 minutes, and then, cooledby blasting air of 10 to 30° C. at a cooling rate of 100 to 300° C./sec.

The air blasting reinforcement process makes the glass plate comprisingNiO and Fe₂O₃ to have the greenish gray and almost neutral shade, and tohave the low visible light transmittance and the low ultraviolettransmittance while keeping the high heat rays absorptivity.

In the present invention, when measured by using C.I.E standardilluminant “A”, the glass with a thickness between 2 to 5 mm has avisible light transmittance (YA) in the range from 10% to 25%, a solarenergy transmittance (TG) in the range from 5% to 20% and an ultraviolettransmittance (Tuv) defined by ISO of not greater than 15%, preferablynot greater than 10%.

In case of using L* a* b* color system, the chromaticity, expressed bya* and b*, of the glass color are preferably in ranges of −10≦a*≦0 and−3≦b*≦7, respectively.

When the glass is used in a rear window of vehicle for the privacyprotection, since almost neutral colored glass is particularlypreferred, the chromaticity is in the ranges of −5≦a *≦0 and 0≦b*≦5.

When measured by using C.I.E. standard illuminant “C” over thewavelength range from 380 to 770 nanometers, the glass of the presentinvention preferably has optical properties with a dominant wavelength(λd) in the range from 480 to 580 nanometers and an excitation purity(Pe) of less than 10%.

EXAMPLES

Hereinafter, the mode of carrying out the present invention will bedescribed referring to some examples.

Examples 1 through 9

Glass raw material is prepared by adding required composition consistingof ferric oxide, titanium oxide, cerium oxide, cobalt oxide, metallicselenium, and nickel oxide into a standard soda-lime-silica glass batchcomposition, also adding carbonaceous reducing agent (concretely, cokepowder etc.) at a ratio of about 0.01 parts by weight per 100 parts ofthe glass raw material therein, and mixing them. The glass raw materialthus prepared is heated and melted in an electric furnace at 1500° C.for 4 hours. The molten glass is flowed onto a stainless plate andannealed to the room temperature to obtain a 6 mm thick glass plate.After polishing the glass plate in such a manner that the thicknessreduces to 4 mm, the glass plate is reinforced with reheating it at 700°C. for 5 minutes and then cooling it with 200° C. air blast at 3.2 to2.1 kgf/mm² wind flow to become a sample. Each sample is measured in thevisible light transmittance by the C.I.E. illuminant A (YA), the solarenergy transmittance (TG), the ultraviolet transmittance by ISO9050(Tuv), the dominant wavelength by the illuminant C(λd), and theexcitation purity (Pe). And, L*, a* and b* are measured followingC.I.E.L.A.B.

Tables 1 and 2 show base glass compositions of the obtained samples,T—Fe₂O₃ concentration, FeO (expressed as Fe₂O₃) concentration, FeO(expressed as Fe₂O₃)/T—Fe₂O₃ rate, CoO concentration, Se concentration,NiO concentration, CeO₂ concentration, and TiO₂ concentration. Thenumerals in Tables are indicated as a percentage of the weight exceptthat CoO concentration, Se concentration, and NiO concentration areexpressed in ppm. Tables 1 and 2 also show the optical properties of therespective samples.

TABLE 1 Exmple 1 2 3 4 base glass composition [wt. %] SiO₂ 71.8 71.071.0 71.8 Al₂O₃ 1.7 1.7 1.7 1.7 MgO 3.8 3.8 3.8 3.8 CaO 7.8 7.8 7.8 7.8Na₂O 13.9 13.9 13.9 13.9 K₂O 1.0 1.0 1.0 1.0 B₂O₃ 0 0.8 0.8 0 T—Fe₂O₃1.25 1.25 1.25 1.25 FeO 0.313 0.315 0.280 0.284 FeO/T—Fe₂O₃ (%) 27.828.0 24.9 25.2 CeO₂ — — — — TiO₂ — — — — Se (ppm) 9 9.5 15 30 CoO (ppm)185 185 180 180 NiO (ppm) 550 600 700 700 optical property YA (%) 19.618.7 16.4 10.9 TG (%) 16.5 15.9 15.7 16.2 Tuv (%) 5.34 5.12 4.18 4.41 L*52.24 51.08 47.59 41.43 a* −6.64 −6.47 −4.02 −4.59 b* −3.38 −1.82 3.872.93 λ d 489.0 491.4 558.1 545.2 Pe (%) 9.30 7.25 5.37 3.59

TABLE 2 Example 5 6 7 8 9 base glass composition [wt. %] SiO₂ 71.8 71.871.8 70.8 70.8 Al₂O₃ 1.7 1.7 1.7 1.7 1.7 MgO 3.8 3.8 3.8 3.8 3.8 CaO 7.87.8 7.8 7.8 7.8 Na₂O 13.9 13.9 13.9 13.9 13.9 K₂O 1.0 1.0 1.0 1.0 1.0B₂O₃ 0 0 0 0 0 T—Fe₂O₃ 1.50 1.35 1.25 1.25 1.25 FeO 0.301 0.300 0.2900.290 0.300 FeO/T—Fe₂O₃ (%) 20.0 22.2 23.2 23.2 22.3 CeO₂ — — — — 1.0TiO₂ — — — 1.0 — Se (ppm) 15 11 12 15 15 CoO (ppm) 180 130 190 185 185NiO (ppm) 700 550 1000 600 600 optical property YA (%) 15.7 22.1 14.815.8 16.0 TG (%) 15.3 17.9 15.0 15.7 15.6 Tuv (%) 3.19 4.70 5.05 2.702.83 L* 46.61 54.14 45.74 47.33 48.01 a* −3.79 −5.00 −5.51 −4.09 −4.02b* 4.45 6.85 2.92 4.82 3.95 λ d 562.2 564.5 535.7 562.2 559.6 Pe (%)6.56 9.27 3.51 7.03 5.92

Table 1 and 2 show that all of the samples of Examples 1 through 9 havethe visible light transmittance (YA) between 10% and 25%, the solarenergy transmittance (TG) between 5% and 20%, and the ultraviolettransmittance (Tuv) less than 15%.

These samples have the chromaticity expressed by a* and b* in ranges of−10≦a*≦0 and −3≦b*≦7, the dominant wavelength (λd) measured by using theilluminant “C” between 480 and 580 nanometers, and excitation purity(Pe) of less than 10%.

As compared with the Example 1 or 2, the glasses of the Example 3-9 havelarge values of a* and have the preferable lighter green shade.

Example 4 is not preferable in view of visibility because of its lowvisible light transmittance due to the large amount of Se.

In examples 2-5 and 7-9, these glasses comprising the sufficient amountof NiO are shown to have preferable properties.

It is shown that Example 8 and 9 have the excellent high ultravioletabsorptivity.

Therefore, when the glass compositions of the examples mentioned aboveare used for windshields of vehicles and windows of buildings, goodeffects of preventing degradation of interior materials and of privacyprotecting can be obtained.

Comparative Examples 1-5

Table 3 shows glass components and optical properties of ComparativeExamples which are made in the same manner as Examples 1-9 but the glasscomponents are different.

TABLE 3 Comparative Example 1 2 3 4 5 base glass composition [wt. %]SiO₂ 71.8 71.7 70.8 71.7(7) 71.7(7) Al₂O₃ 1.7 1.7 1.7 1.7 1.7 MgO 3.83.8 3.8 3.8 3.8 CaO 7.8 7.8 7.8 7.8 7.8 Na₂O 13.9 13.9 13.9 13.9 13.9K₂O 1.0 1.0 1.0 1.0 1.0 B₂O₃ 0 0 1.0 0 0 T—Fe₂O₃ 1.12 1.38 1.653 1.250.80 FeO 0.388 0.210 — 0.301 0.176 FeO/T—Fe₂O₃ (%) 38.5 16.9 21.9 26.722.0 CeO₂ — — — — — TiO₂ — 0.10 — 0.03 0.03 Se (ppm) 19 43 20 15 11 CoO(ppm) 114 235 236 90 180 NiO (ppm) — — 256 600 700 optical property YA(%) 24.1 17.1 16.0 22.5 20.0 TG (%) 16.1 16.6 13.4 18.1 34.7 Tuv (%)14.3 2.50 7.90 4.21 8.93 L* — — 47.1 53.99 52.09 a* — — −4.32 −1.38−4.25 b* — — 4.55 11.77 2.45 λ d 491.6 530 560.1 575.4 540.2 Pe (%) 3.883.90 6.50 18.09 2.72

All of Comparative Examples 1-5 have compositions out of the range ofthe present invention. Comparative Example 1 has the same composition asthe example of Japanese Patent H7-29813B, which shows the glass producedby the vacuum refining process, as referred in the prior artdescription. Comparative Example 2 has the same composition as theexample of Japanese Patent H8-157232A as referred above. ComparativeExample 3 has the same composition as the example of PCT (Japanesephase) H7-508971 as referred above.

It should be noted that the optical properties of Comparative Example 1are indicated in values converted based on a glass thickness of 3.9 mmand the optical properties of Comparative Example 2 are indicated invalues converted based on a glass thickness of 5 mm.

Comparative Example 4 contains CoO as a colorant of which amount is outof the scope of the present invention, Comparative Example 5 containsT—Fe₂O₃ amount of which is out of the scope of the present invention.

It is apparent from Table 3 that as compared with the examples of thepresent invention, Comparative Examples 1 has a very large value ofFeO/T—Fe₂O₃ ratio in order to improve the heat rays absorptivity withoutincluding NiO. The glass of Comparative Example 1 is unpreferable to beproduced in an ordinary melting furnace.

The glass of Comparative Example 2 which does not comprise NiO isrequired to comprise a large amount of Se and CoO to provide thedesirable color shade and optical properties.

As compared with the present invention, the glass of Comparative Example3 comprising a low amount of Nia and a large amount of T—Fe₂O₃ hasdifficulties to be produced in ordinary melting furnace.

Comparative Examples 4 has an amount of CoO out of scope of the presentinvention, so that the obtained shade is unpreferablly yellow tint.

Comparative Examples 5 contains T—Fe₂O₃ an amount of which is out of theclaimed range so that it can not obtain sufficient heat raysabsorptibity.

As detailed above, according to the present invention, anultraviolet/infrared absorbent low transmittance glass, which exhibitslow visible light transmittance, low solar energy transmittance, and lowultraviolet transmittance and which has greenish gray shade can beprovided.

The ultraviolet/infrared absorbent low transmittance glass having thegreenish gray shade can exhibit the effect of preventing degradation anddiscoloration of interior materials and the privacy protecting effectwhen the glass is used for a rear window glass of a vehicle, a window ofa building, or the like.

What is claimed is:
 1. An ultraviolet/infrared absorbent lowtransmittance glass consisting of base plate and colorants, said baseglass comprising: 60 to 85 wt. % SiO₂; 0 to 5 wt. % Al₂O₃; 0 to 10 wt. %MgO; 5 to 15 wt. % CaO wherein a total amount of MgO and CaO is between5 and 15 wt. %; 10 to 18 wt. % Na₂O; 0 to 5 wt. % K₂O wherein a totalamount of Na₂O and K₂O is between 10 and 20 wt. %; and 0 to 5 wt. %B₂0₃, said colorants comprising: 1.25 to 1.5 wt. % total iron oxide(T—Fe₂O₃) expressed as Fe₂O₃; 0.01 to 0.019 wt. % CoO; more than 0.001wt. % and equal to or less than 0.003 wt.% Se; and 0.06 to 0.1 wt. %NiO, wherein said glass with a thickness between 2 and 5 mm has avisible light transmittance (YA) by the C.I.E. illuminant “A” in a rangefrom 10% to 25%, a solar energy transmittance (TG) in a range from 5% to20%, and an ultraviolet transmittance (Tuv) of not more than 15%specified by ISO.
 2. An ultraviolet/infrared absorbent low transmittanceglass as claimed in claim 1, wherein FeO expressed as Fe₂O₃ is between15 wt. % and 40 wt. % of T—Fe₂O₃.
 3. An ultraviolet/infrared absorbentlow transmittance glass as claimed in claim 1, wherein Se is between0.001 wt. % and 0.0018 wt. %.
 4. An ultraviolet/infrared absorbent lowtransmittance glass as claimed in claim 1, wherein said colorant furthercomprises at least one of CeO₂ of no greater than 2 wt. % and TiO₂ of nogreater than 2 wt. %.
 5. An ultraviolet/infrared absorbent lowtransmittance glass as claimed in claim 4, wherein the glass has a colordefined by the following C.I.E.L.A.B. coordinates −5 ≦a*≦0 and 0 ≦b*≦5.6. An ultraviolet/infrared absorbent low transmittance glass as claimedin claim 1, wherein the glass has a color defined by the followingC.I.E.L.A.B. coordinates −10≦a*≦0 and −3≦b*≦7, and an almost neutralcolor of greenish gray.
 7. An ultraviolet/infrared absorbent lowtransmittance glass as claimed in claim 1, wherein the glass isreinforced by air blast cooling.
 8. An ultraviolet/infrared absorbentlow transmittance glass as claimed in claim 7, wherein the glass plateproduced from the molten glass is reheated at 600 to 750° C. for 2 to 5minutes and then cooled by blasting air of 10 to 30° C. at a coolingrate of 100 to 300° C./sec in the reinforcement process.
 9. Anultraviolet/infrared absorbent low transmittance glass as claimed inclaim 1, wherein Al₂O₃ is between 0.1 wt. % and 2 wt. %.
 10. Anultraviolet/infrared absorbent low transmittance glass as claimed inclaim 1, wherein the glass has an ultraviolet transmittance of nogreater than 10%.
 11. An ultraviolet/infrared absorbent lowtransmittance glass as claimed in claim 1, wherein the glass with athickness of 4 mm has a dominant wavelength of 480 to 580 nanometerswith the using C.I.E. standard illuminant “C” over the wavelength rangefrom 380 to 770 nanometers and an excitation purity of less than 10%.12. An ultraviolet/infrared absorbent low transmittance glass as claimedin claim 1, wherein the glass has a greenish gray color, and the glasswith a thickness of 4 mm has a dominant wavelength between about 535.7and 580 nanometers when measured by using C.I.E. standard illuminant “C”over a wavelength range from 380 to 770 nanometers.